Generally, there are three piston rings used in a cylinder of an internal combustion engine: the top ring, the second ring, and the oil ring. The three piston rings are positioned around a piston capable of reciprocal movement within the cylinder. For example, the piston is cylindrical, and the top ring, the second ring, and the oil ring are respectively spaced in vertically descending order there along. The combination of all three piston rings serves to isolate the combustion chamber from the crankcase.
The top ring serves two purposes: preventing gases (from the combustion chamber) from passing there around, and transferring heat from the piston to the engine block through the walls of the cylinder. The oil ring prevents oil (from the crankcase) from passing there around. The second ring compliments both the top ring and the oil ring. The second ring prevents gases (which bypassed the top ring) from passing there around, and prevents oil (which bypassed the oil ring) from passing there around. Consequently, the top ring, the second ring, and the oil ring are seals for preventing the passage of gases and/or oil. Without the isolation of the combustion chamber and the crankcase provided by the piston rings, the presence of gases in the crankcase and oil in the combustion chamber would decrease the horsepower of the internal combustion engine.
To serve as seals, the top ring and second ring springingly engage the walls of the cylinder. For example, in the “free state” before installation, the top ring and second ring are biased to expand. That is, the top ring and second ring have expanded diameters forming a gap between their respective ends. When the top ring and second ring are installed around the piston, the ends of each ring are squeezed together. Thereafter, the piston and the surrounding rings are inserted into the cylinder. Because each ring is biased to expand toward its “free state,” the top ring and the bottom ring expand against the walls of the cylinder. As such, the top ring and the bottom ring springingly engage the walls of the cylinder, and serve to effectuate the above-discussed seal between the combustion chamber and the crankcase.
For normal use, it is generally unnecessary to “fit” the gaps between the ends of the top ring and the second ring to precise tolerances. However, for high performance/racing applications, fitting the gaps can used provide a competitive advantage. For example, the top rings and the second rings used in racing applications are often sold with oversized dimensions, and, therefore, provide small gaps between their ends. Consequently, before installation, the ends of the top rings and second rings can be filed and refiled to provide gaps of different sizes. Such different sized gaps provide for different separations between the ends when the piston rings are installed.
The filing and refiling allows the performance of the various gap sizes (and corresponding separations) to be tested, and such experimentation can enhance the performance of an internal combustion engine. For example, because internal combustion engines used in racing operate at high temperatures, it is necessary to provide a gap allowing for expansion of the piston rings according to the high temperatures. Thus, a properly sized gap would allow the ends to be initially separated when the piston rings are inserted into the cylinder, which separation could thereafter close when the piston rings expand due to exposure to high temperatures.
However, if the gaps are sized too small, the ends will close before the piston rings are finished expanding, and the piston rings will warp, thereby causing “scuffing” of the walls of the cylinder. Moreover, if the ends are misaligned, the ends will touch unevenly, which will not only cause unwanted separation therebetween before the piston rings are finished expanding, but which might also force the piston rings to expand awkwardly, thereby also causing “scuffing” of the walls of the cylinder. Consequently, the gaps must be precisely sized, and the ends must be properly aligned with respect to one another.
At present, most known manually operated devices which assist in the grinding of the ends of the piston rings rely on the manual placement and holding of the ring. That is, one hand of the user attempts to steadily hold the ring while the other hand performs the grinding process. But such manual operation has been found not to provide for continued, repeated, accurate grinding. Moreover, such manual devices do not readily accommodate piston rings of varying sizes.